The invention relates to a motor vehicle seat.
A motor vehicle seat of this kind comprises a seat frame; a pivotally mounted back rest of the seat frame which can be adjusted on one side (by pivoting) in an area of use between different useful positions and which on the other side—after releasing the backrest, for example by means of a release lever normally provided for this on the backrest—can be folded forwards (by pivoting) steplessly towards the seat surface of the seat frame; a seat longitudinal guide for adjusting the seat longitudinal position of the seat frame; a fixing device for locking a previously set seat longitudinal position; a coupling mechanism through which the backrest is coupled to the fixing device so that when the backrest is folded forwards towards the seat surface the fixing device can be released by an output side of the coupling mechanism; as well as a tumbler fitment of the backrest which when pivoting the backrest tumbles about a tumbler axis and to which an input side of the coupling mechanism is connected.
The different useful positions which the seat back can occupy in the area of use serve to support the back of a person seated on the seat. Further useful positions can also serve to support the back of a person reclining on the seat.
Folding the backrest onto the seat surface, on the other hand, serves to release the fixing device of the seat longitudinal guide through the coupling mechanism which is connected on the input side to the tumbler fitment and on the output side to the fixing device. Folding the backrest forwards is normally accomplished by actuating a lever provided for this purpose on the backrest which enables the backrest to be folded effortlessly forwards onto the seat surface whilst at the same time releasing the useful position of the vehicle seat which previously existed.
After releasing the fixing device by folding the backrest forwards the seat can be easily moved forwards, for example, to facilitate ease of entry into the back of the vehicle in the case of a two-door cabriolet vehicle. This is the so-called easy-entry function which is to make access to the back seat of a two-door vehicle that much easier. This easy-entry function is often coupled to a memory device through which the original seat position is automatically relocated when subsequently sliding back the vehicle seat.
In the case of a known vehicle seat of the type mentioned at the beginning, the coupling mechanism comprises a Bowden cable whose core is connected on one side to the tumbler fitment and on the other side (if necessary through further coupling elements) to the fixing device of the seat longitudinal guide. The problem here is that as a result of the tumbler movement of the tumbler fitment when swiveling the seat—depending upon the useful position in which the seat is already located—there is a different lengthening of the Bowden cable and thus different operating paths arise for releasing the fixing device by means of the Bowden cable. In order to solve this problem it is known to integrate an elastic element in the form of a tensile spring into the core of the Bowden cable whereby the spring constant of this spring is so great that it does not impair the actuation of the fixing device by means of the Bowden cable. The action of this spring must thus overcome the action of the spring elements normally integrated into the fixing device whose function is to pretension the fixing device into its locked state. (Through this pretensioning of the fixing device into its locked state it is to be guaranteed for safety reasons that the seat longitudinal guide is always then automatically locked unless an occupant actively actuates the release of the fixing device). Only if the fixing device is fully unlocked and further actuation of the fixing device by means of the coupling mechanism is no longer possible does the tensile spring expand and thus permit compensation of the overtravel which can happen as a result of the previously mentioned different actuating paths for releasing the fixing device—depending on the position of the seat back and thus the tumbler fitment at the start of folding the backrest forwards.
The known coupling mechanism for the easy-entry function has the drawback that as a result of the large spring constant required the spring which is to be integrated for this into the Bowden cable takes up some structural space and significantly increases the weight of the assembly.